The present invention relates to positioning apparatus in general, and to relatively compact apparatus for controlling movement of a positioning device commonly referred to as an industrial robot, in particular.
Automated product assembly machines, for example, have been employed in manufacturing industries for a great number of years. More recently, though, technologically more sophisticated machines have been employed for such purposes. These more recent machines are commonly referred to as industrial robots. Industrial robots are capable of performing various mechanical operations with a high degree of speed and accuracy in response to a set of programmed instructions.
Common uses for industrial robots include the movement of a workpiece from one position to another and the performance of repetitive operations with a high degree of precision. The use of industrial robots in place of human personnel has proven very beneficial in that they have resulted in both cost reductions and processing accuracy and have relieved many personnel from routine and/or potentially hazardous jobs. Industrial robots are also employed in numerous other fields of technology to perform a variety of different operations.
A significant problem associated with industrial robots, especially those employed for product assembly purposes, is their inability to recognize when they collide or make contact with objects located in their path of travel when moving to perform programmed tasks. Inasmuch as most industrial robots are capable of generating extremely large physical forces, such forces can seriously damage or even destroy such contacted objects, objects that have heretofore been undetectable when struck or contacted by any portion of a moving robot. A typical object damaging situation often occurs when an industrial robot is programmed to place a series of identical objects or piece-parts into fairly close tolerance openings or recesses in, for example, a series of housings, during product assembly, over an extended period of time. During this extended period of product assembly time, a gradual misalignment will often result between, for example, the center of the housing opening and the center of the piece-part that is being inserted into the housing opening. Such misalignment has heretofore been undetectable by an industrial robot. The consequences of the industrial robot being unable to detect such misalignment often are damage to the piece-part and/or to the housing, or to the robot itself because of the large physical forces that are sometimes generated by a robot as it blindly attempts to place a piece-part in a misaligned housing opening where it is incapable of detecting such misalignment.
In U.S. patent application Ser. No. 484,228 by M. KHUSRO, filed on the same date as the present application, robot arm member relative movement sensing apparatus is disclosed that determines when a relatively movable driven robot arm member moves out of positional alignment with a driving robot arm member. The apparatus includes a light source mounted on one member and a light sensitive device mounted on the other member that is capable of continuously generating a member-to-member relative position signal in response to light from said light source being optically focused on said light sensitive device. Relative movement between these two robot arm members causes the light sensitive device to generate an electrical signal representative of the extent of member-to-member relative movement However, by employing a conventional optical lens to focus a portion of the light from the light source onto a surface of the light sensitive device, the lens element must be spaced a relatively large distance from the light sensitive device surface in order to place the light sensitive surface at the lens element focal plane for proper light sensitive device operation. Providing this required space necessarily increases relative movement sensing apparatus size and/or length. In addition, the light focusing lens element mounting must be substantial enough to maintain the lens light path in a predetermined, relatively fixed orientation during robot arm operation including operations in a mechanical shock or highly vibratory environment. A lens element of a size employed in the above-noted patent application presents difficult mounting problems for a lens that must operate in such an environment.
A primary object of the present invention is to provide compact apparatus for detecting relative movement between members that are resiliently attached to one another.
Another object of the present invention is to provide relative movement sensing apparatus that can operate in a vibratory environment.
Still another object of the present invention is to provide compact apparatus for determining when a portion of an industrial robot arm comes in contact with a robot arm motion impeding object.
A further object of the present invention is to provide compact apparatus that will enable an industrial robot to apply a predetermined physical force to a particular object or workpiece, such as when forcing components together during product assembly, with a predetermined force.
Other objects, features and advantages of the present invention will be readily apparent from the following detailed description of the preferred embodiment thereof taken in conjunction with the accompanying drawings.